In-situ alloying of nonequiatomic TiNbMoTaW refractory bio-high entropy alloy via laser powder bed fusion: Achieving suppressed microsegregation and texture formation

Abstract

High-entropy alloys (HEAs) have attracted considerable attention owing to their excellent properties. However, the severe segregation of the constituent elements remains a common challenge in refractory HEAs. Recently, an approach to suppress segregation was proposed using laser powder bed fusion (LPBF) owing to the ultra-high cooling rates during solidification. Despite the advantages of LPBF, the persistent microsegregation between the dendritic and interdendritic regions of refractory HEAs and costly gas atomization process hinder the further development. To address these challenges, a novel nonequiatomic TiNbMoTaW refractory HEA was designed to minimize the difference between the liquidus and solidus temperatures to prevent segregation and phase separation for a better biological performance. In-situ alloying was implemented instead of costly and time-consuming gas atomization process. The segregation of constituent elements was suppressed by remelting, resulted in epitaxial growth and development of crystallographic texture, consequently reducing residual stress. The mechanical properties were improved due to the increase of solid solution strengthening and densification. It showed superior mechanical strength and equivalent biocompatibility compared to conventional biomaterials, indicating its superiority as a biomaterial. This study represents the first successful control of crystallographic texture through in-situ alloying of BioHEAs for next-generation biomaterials.